The topic of handrail design came up yesterday, and I did a quick pole to find out what folks are up to on this front.
Interesting...
The design forces for the railing are typically indicated in the code - ASCE 7-05 [4.4.1] talks about the loads, and some exceptions for SFR.
In IBC 2006 and previous, [1607.7.1.3] used to talk about a 1/3 stress increase for members and their attachments wrt (with respect to) handrail design. In IBC 2009, this has been removed - drat! (i'm not sure that we were all taking advantage of this stress increase when we had it).
So the question came up about whether the load for handrails referred to in the code was indeed a "live" load, or more of an "impact" load? For wood design, Cd for impact is 2.0, while for live, it is 1.0. Since "common sense" would indicate that handrails loads are not likely to a sustained loading condition, it could be argued that a stress increase could be appropriate - and may be necessary - in order to come up with a reasonable solution.
Maybe we should consider getting the commentary on this section to see why they removed the section.
Any comments?
Interesting...
The design forces for the railing are typically indicated in the code - ASCE 7-05 [4.4.1] talks about the loads, and some exceptions for SFR.
In IBC 2006 and previous, [1607.7.1.3] used to talk about a 1/3 stress increase for members and their attachments wrt (with respect to) handrail design. In IBC 2009, this has been removed - drat! (i'm not sure that we were all taking advantage of this stress increase when we had it).
So the question came up about whether the load for handrails referred to in the code was indeed a "live" load, or more of an "impact" load? For wood design, Cd for impact is 2.0, while for live, it is 1.0. Since "common sense" would indicate that handrails loads are not likely to a sustained loading condition, it could be argued that a stress increase could be appropriate - and may be necessary - in order to come up with a reasonable solution.
Maybe we should consider getting the commentary on this section to see why they removed the section.
Any comments?
2 comments:
For a welded handrail system, I have designed based on a 200 plf railing load be distributed half to a center post and 1/4 each to two adjacent posts (three posts considered in analysis) which reduced the overturning moment and therefore connection forces.
Does the 2003 IBC commentary discuss the previous stress increase factor?
Anne McAteer-Berg, PE, SE
amcateer-berg@ctengineering.com
==========
I checked the IBC 2003 commentary - its benign. Talks about OK to use stress increase since the loads are maximum anticipated...
Would be more interested to know why they removed it !
Cheers RT
Along the same lines... we are being dragged into design of deck connections for a Julliete balcony arrangement. There is an interest to have a bolt-on kerf plate that the deck connects to.
I have run some numbers. The deck appears to work quite comfortably (unless i'm missing something!). I scanned some quick calcs and a drafted detail that i propose to use on Ash Way. (located here: G:\LIBRARY\DETAILS\Julliette Balcony) [unfortunately i can't place live links in a comment to a blog... ]
What do y'all think about it...? Please comment if you spot anything out of whack!
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